The present invention relates to knives having one or more blades pivotally movable between open and closed positions, and more particularly to novel structure for retaining a folding knife blade in the open position until manually released.
In one form of so-called pocket knives, the blade or blades are movable about a pivot pin between open and closed positions with respect to a handle piece. In the fully open position the blade(s) extend substantially linearly from the handle, and in the closed position at least a portion including a sharpened edge is positioned in a space provided for such purpose between two portions of the handle. The open position of the blade(s) is usually defined by engagement of a locking surface (e.g., a shoulder or notch) formed in the blade with stationary structure on or connected to the handle. In order to ensure that the blade does not move from the fully open toward the closed position inadvertently, as when pressure is applied to the back of the blade while in use, it has been a common practice to provide folding knives with a so-called xe2x80x9clock-backxe2x80x9d feature. The prior art includes lock-back structures which require manipulation by the user both for activating and deactivating the locking feature, as well as those which operate automatically, as by spring bias, upon movement of the blade to the open position. It is with the latter type of lock-back mechanism with which the present invention is concerned.
The object of the invention is to provide a folding blade knife having novel and improved structure which is automatically operable upon movement of the blade(s) to the fully open position to prevent movement away from such position, and which is quickly and easily manually manipulated to permit movement from open to closed position when desired.
Other objects will in part be obvious and will in part appear hereinafter.
In the disclosed embodiment, the knife of the invention has but a single blade although it will be immediately recognized and understood that a plurality of blades, tools, or the like, each movable between fully open and closed positions with respect to a handle piece, may be provided within the scope of the invention. The disclosed blade has a sharpened edge and a back, blunt edge. The blade has the usual tang portion at its proximal end, and is supported by a pivot pin passing through the tang and anchored in spaced portions of the handle piece. Each of the two handle portions includes a liner and a cover piece. A locking arm is pivotally mounted by a pin in one of the cover pieces and extends through a slot in the adjacent liner, across the space between the two liners, through a slot in the other liner and terminates at a manually engageable head in a slot in the other cover piece.
A plunger and spring are positioned in a recess in the other cover piece facing the adjacent liner. The plunger urges the locking arm toward rotation to a position wherein the portion of the arm spanning the space between the two cover portions blocks movement of the blade tang in the direction in which it must move to close the blade. That is, when the blade is in its fully open position the locking arm is moved, by the spring biased force of the plunger, to a position directly in the path in which the tang must be moved in order to move the blade away from the open position, thus preventing inadvertent, closing movement of the blade with possible injury to the user. When it is desired to close the blade, the head on the locking arm is moved within its slot to pivot the arm away from its blocking position against the spring bias.
The foregoing and other features of construction and operation of the lock-back structure of the invention will be more readily understood and fully appreciated from the following detailed disclosure, taken in conjunction with the accompanying drawing.